1. Field of the Invention
The invention relates to a binary analog-digital converter, i.e. one which is capable of converting arbitrary analog quantities into digital signals expressed in a binary code.
The vast majority of physical quantities or parameters being currently examined are most frequently available in analog form. The use and processing of analog data, however, is difficult and subject to errors, drift or distortion. Furthermore, the signals representing these data are generally afflicted with noise, which may be difficult to eliminate. Therefore, it is preferred to use these data in digital form, because the processing of digital signals does not give rise to errors or drift and is less susceptible to noise and distortion.
2. Description of the Prior Art
In principle two types of converters are known which are capable of converting analog quantities into digital signals: the serial or successive-approximation converters, which employ one comparator per bit (or, if the conversion speed is not essential, a single comparator whose output is stored) and in which the digital signal is not available until after a certain number of clock cycles proportional to the number of bits (in fact, the complete settlement of a comparator should be awaited before proceeding to the next bit), and parallel converters which employ as many comparators as there are quantization steps (i.e. 2.sup.n comparators in an n-bit converter) and which are also called asynchronous (instead of appearing only after a specific number of clock cycles, the digital signal closely follows the analog quantity to be transformed, obviously up to a certain frequency limit). The analog-digital converter which is the subject of the present Application belongs to this second category of asynchronous converters.
In an increasing number of industrial fields and in particular in that of television, automobiles, or other mass products employing electronics, it is essential to have analog-digital converters which are fast, have a low power consumption, which can be integrated and which are inexpensive. The slower serial converters cannot be used for such applications; the parallel converters, which are satisfactory in respect of the speed, have the drawback of a large number of components, so that they are complex and difficult to realize, which is rather costly.